there have been a few mods carried out over the years, such as coupler heaters, and coupler pin maintenance which won’t be replicated on the 4’s.
I don’t know how much coupling and uncoupling went on with them on TPE but it was no doubt nowhere near the three or four times a day it can happen on WMT
Coupling on TPE has obviously reduced with the reduction of the fleet size but they often come and go off depot coupled, as required.
From what I can gather there are two tasks on the couplers that aren't on the /4 schedule. One task involves replacing electrical contacts (specifically ones which connect the TMS between units) and the other is electrical head guide pin and bush renewal, both done every 5 years and both can be done in a short amount of time. Other light coupler maintenance (exams) seem to be on par with the other 350s.
I can't see any documents to suggest any coupler modifications. CCU/TMS software has been updated though, which appears to be for compatability with the TOC (and maybe for working with /2s too).
Also, the /4s already have heaters fitted and are switched on over winter.
Batteries have always been an issue with these. Having spoke to someone from Kings Heath it seems the /3s and /4s have different cells to the rest which are apparently better. I've always had trouble keeping them powered on batts only while getting them onto the non-electrified wheel lathe / bogie drop roads. If they've not been disposed of properly by train crew, they go flat and a few tricks have to be carried out to nurse them back to life again! Always trip F10...